The invention relates to a method of producing glass vials, in particular pharmaceutical vials or pharmaceutical ampoules, as well as a glass vial produced thereby.
Glass bottles that are used for pharmaceutical purposes (also known as so-called “vials”) consist of neutral glasses, i.e. glasses that can be assigned to the hydrolytic class 1, to this end also the normalized test ISO 719 (DIN 12111) is used. In particular borosilicate glasses, such as a DURAN® or Fiolax® (both registered trade-marks of SCHOTT AG, Mainz) belong to the neutral glasses.
Pharmaceutical vials, or pharmaceutical ampoules, respectively, in addition must have an alkali emission as low as possible, wherein measurement is performed according to the normalized test ISO 4802. In addition, so-called delaminations must be avoided, i.e. flake-offs of regions on the glass surface which result in particular from glass components evaporated during hot-forming and precipitated on the glass surface. Namely, in the worst case such delaminations could enter into the contents of the pharmaceutical vials and could thus spoil the content.
According to the prior art pharmaceutical vials usually are prepared from borosilicate glass by hot-forming a borosilicate glass tube. Herein firstly from the open tube end the orifice of the vial is formed. Thereafter the vial bottom is formed and simultaneously the vial is separated from the residual of the glass tube.
The production of pharmaceutical vials is performed in several steps. Usually, in a first step a glass tube is secured in an upper and a lower chuck and then rotated. The rotating glass tube in a certain region is heated by one or two separating burners so far that it becomes deformable. As soon as this temperature is reached, the tube—under continuing rotation and heating by means of the burner—is extended in axial direction by means of a linear movement of the lower chuck. Thereby the tube in the heated region extends under simultaneous tapering of its diameter, so that a constriction region results. After the upward movement the construction area is further heated. In this way the glass tube at the constriction region further contracts by means of the flow pressure of the burner gases so that the glass walls in the heated region melt together and finally the connection between the upper and the lower tube region pulls off.
Thus two tube sections with closed ends are generated, wherein the upper tube section is the final vial, and the lower tube section is the residual glass tube from which further vials can be formed. In a subsequent step below the upper tube section a so-called “piercing burner” is placed to melt again the bottom of the upper tube section. Also during this procedure the upper tube section is rotated.
This is basically known from U.S. Pat. No. 2,935,819.
From EP-A-2 239 237 this production method is also known. Accordingly, in the beginning the orifice of the vial is formed and thereafter the bottom. During bottom forming the glass tube must be heated to a higher temperature, and thus alkali borate components can evolve from the glass tube and can precipitate on the inner surface of the vial. Thus a modified region on the inner surface of the glass vial results from which alkali components can be easily leached and which also tends to delaminate.
For reducing the alkali leaching also treatments with sodium sulphate or a CVD coating of the inner surface with a thin quartz layer are known.
According to US-A1-2009/0099000 it is tried to reduce the alkali evaporation by reversing the production steps during the vial production. Accordingly, in the beginning the bottom shall be formed, only thereafter the vial neck is formed. A further reduction of the alkali evaporation shall be reached by an additional treatment of the inner surface by means of a flame during the bottom forming.
According to EP-A-2 239 237 it is suggested for reducing the alkali leaching to treat the inner surface of the glass vial by means of a burner flame to remove alkali or similar components sticking thereto.
Thereby alkali leaching shall be reduced.
The known production methods on the one hand are relatively tedious or on the other hand lead to results, wherein the alkali elution is still too high.